Multi-speed transmission

ABSTRACT

A transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may include clutches and brakes.

FIELD

The invention relates generally to a multiple speed transmission havinga plurality of planetary gear sets and a plurality of torquetransmitting devices and more particularly to a transmission havingeight or more speeds, four planetary gear sets and a plurality of torquetransmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of frictionclutches, planetary gear arrangements and fixed interconnections toachieve a plurality of gear ratios. The number and physical arrangementof the planetary gear sets, generally, are dictated by packaging, costand desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission is provided having an input member, an output member,four planetary gear sets, a plurality of coupling members and aplurality of torque transmitting devices. Each of the planetary gearsets includes first, second and third members. The torque transmittingdevices are for example clutches and brakes.

An embodiment of the transmission includes four planetary gear sets,three clutches and two brakes.

It is thus an object of the present invention to provide a transmissionhaving four planetary gear sets.

It is a further object of the present invention to provide atransmission having at least eight forward speeds and at least onereverse.

It is a still further object of the present invention to provide atransmission having four planetary gear sets, a plurality of couplingmembers and a plurality of torque transmitting devices.

Further objects, aspects and advantages of the present invention willbecome apparent by reference to the following description and appendeddrawings wherein like reference numbers refer to the same component,element or feature.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of an eight speedtransmission according to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of an eight speedtransmission according to the present invention; and

FIG. 3 is a truth table presenting the state of engagement of thevarious torque transmitting clutches in each of the available forwardand reverse speeds or gear ratios of the transmission illustrated inFIGS. 1 and 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that in the particular exampleprovided, the eight speed automatic transmission of the presentinvention has an arrangement of permanent mechanical connections betweenthe elements of the four planetary gear sets. A first component orelement of a first planetary gear set is permanently coupled to a secondcomponent or element of a second planetary gear set. A third componentor element of the second planetary gear set is permanently coupled to afirst component or element of the third planetary gear set. A thirdcomponent or element of the first planetary gear set is permanentlycoupled to a first component or element of a fourth planetary gear set.Finally, a second component or element of the fourth planetary gear setis permanently coupled to a second component or element of a thirdplanetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10is illustrated in a lever diagram format. A lever diagram is a schematicrepresentation of the components of a mechanical device such as anautomatic transmission. Each individual lever represents a planetarygear set wherein the three basic mechanical components of the planetarygear set are each represented by a node. Therefore, a single levercontains three nodes: one for the sun gear, one for the planet gearcarrier, and one for the ring gear. The relative length between thenodes of each lever can be used to represent the ring-to-sun ratio ofeach respective gear set. These lever ratios, in turn, are used to varythe gear ratios of the transmission in order to achieve appropriateratios and ratio progression. Mechanical couplings or interconnectionsbetween the nodes of the various planetary gear sets are illustrated bythin, horizontal lines and torque transmitting devices such as clutchesand brakes are presented as interleaved fingers. If the device is abrake, one set of the fingers is grounded. Further explanation of theformat, purpose and use of lever diagrams can be found in SAE Paper810102, “The Lever Analogy: A New Tool in Transmission Analysis” byBenford and Leising which is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a firstplanetary gear set 14 having three nodes: a first node 14A, a secondnode 14B and a third node 14C, a second planetary gear set 16 havingthree nodes: a first node 16A, a second node 16B and a third node 16C, athird planetary gear set 18 having three nodes: a first node 18A, asecond node 18B and a third node 18C, a fourth planetary gear set 20having three nodes: a first node 20A, a second node 20B and a third node20C and an output shaft or member 22.

The input member 12 is coupled to the second node 14B of the firstplanetary gear set 14. The output member 22 is coupled to the secondnode 18B of the third planetary gear set 18. The first node 14A of thefirst planetary gear set 14 is coupled to second node 16B of the secondplanetary gear set 16. The third node 14C of the first planetary gearset 14 is coupled to the first node 20A of the fourth planetary gear set20. The third node 16C of the second planetary gear set 16 is coupled tothe first node 18A of the third planetary gear set 18. The second node18B of the third planetary gear set 18 is coupled to the second node 20Bof the fourth planetary gear set 20.

A first clutch 26 selectively connects the input member 12 and thesecond node 14B of the first planetary gear set 14 to the first node 16Aof the second planetary gear set 16. A second clutch 28 selectivelyconnects the first node 16A of the second planetary gear set 16 to thethird node 14C of the first planetary gear set 14 and the first node 20Aof the fourth planetary gear set 20. A third clutch 30 selectivelyconnects the first node 16A of the second planetary gear set 16 to thethird node 20C of the fourth planetary gear set 20. A first brake 32selectively connects the second node 16B of the second planetary gearset 16 to a ground or transmission housing 50. A second brake 34selectively connects the third node 18C of the third planetary gear set18 to the ground or transmission housing 50.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 10 according to thepresent invention. In FIG. 2, the numbering from the lever diagram ofFIG. 1 is carried over. The clutches and couplings are correspondinglypresented whereas the nodes of the planetary gear sets now appear ascomponents of planetary gear sets such as sun gears, ring gears, planetgears and planet gear carriers.

For example, the planetary gear set 14 is a planetary gear set thatincludes a sun gear member 14A, a planet gear carrier member 14B and aring gear member 14C. The sun gear member 14A is connected for commonrotation with a first shaft or intermediate member 42. The ring gearmember 14C is connected to a second shaft or intermediate member 44 andto a third shaft or intermediate member 46. The planet gear carriermember 14B rotatably supports a set of planet gears 14D (only one shown)and is connected for common rotation with input shaft or member 12 and afourth shaft or intermediate member 48. The planet gears 14D areconfigured to intermesh with the sun gear member 14A and the ring gearmember 14C.

The input shaft or member 12 is continuously connected to an engine (notshown) or to a turbine of a torque converter (not shown). The outputshaft or member 22 is continuously connected with the final drive unitor transfer case (not shown).

The planetary gear set 16 is a planetary gear set that includes a sungear member 16A, a planet carrier member 16B that rotatably supports afirst set of planet gears 16D and a second set of planet gears 16E, anda ring gear member 16C. The sun gear member 16A is connected for commonrotation with a fifth shaft or intermediate member 52. The planetcarrier member 16B is connected for common rotation to the first shaftor intermediate member 42. The ring gear member 16C is connected forcommon rotation with a sixth shaft or intermediate member 54. The firstset of planet gears 16D are configured to intermesh with both the ringgear member 16C and the second set of planet gears 16E. The second setof planet gears 16E are configured to intermesh with both the sun gearmember 16A and the first set of planet gears 16D.

The planetary gear set 18 is a planetary gear set that includes a sungear member 18A, a ring gear member 18C and a planet carrier member 18Bthat rotatably supports a set of planet gears 18D. The sun gear member18A is connected for common rotation with sixth shaft or intermediatemember 54. The ring gear member 18C is connected for common rotationwith a seventh shaft or intermediate member 56. The planet carriermember 18B is connected for common rotation with the output shaft ormember 22. The planet gears 18D are configured to intermesh with bothsun gear member 18A and ring gear member 18C.

The planetary gear set 20 is a planetary gear set that includes a sungear member 20A, a ring gear member 20C and a planet carrier member 20Bthat rotatably supports a set of planet gears 20D. The sun gear member20A is connected for common rotation with second shaft or intermediatemember 44. The ring gear member 20C is connected for common rotationwith an eighth shaft or intermediate member 58. The planet carriermember 20B is connected for common rotation with output shaft 22. Theplanet gears 20D are configured to intermesh with both the sun gearmember 20A and the ring gear member 20C.

The torque-transmitting mechanisms or clutches 26, 28, 30 and brakes 32and 34 allow for selective interconnection of the shafts orinterconnecting members, members of the planetary gear sets and thehousing. For example, the first clutch 26 is selectively engageable toconnect the fourth shaft or intermediate member 48 to the fifth shaft orintermediate member 52. The second clutch 28 is selectively engageableto connect the third shaft or intermediate member 46 to the fifth shaftor intermediate member 52. The third clutch 30 is selectively engageableto connect the fifth shaft or intermediate member 52 to the eighth shaftor intermediate member 58. The first brake 32 is selectively engageableto connect the first shaft or intermediate member 42 to ground ortransmission housing 50 in order to restrict planet carrier member 16Band sun gear member 14A from rotating relative to the ground ortransmission housing 50. The second brake 34 is selectively engageableto connect the seventh shaft or intermediate member 56 to ground ortransmission housing 50 in order to restrict ring gear member 18C fromrotating relative to the ground or transmission housing 50.

Referring now to FIGS. 2 and 3, the operation of the embodiment of theeight speed transmission 10 will be described. It will be appreciatedthat transmission 10 is capable of transmitting torque from the inputshaft or member 12 to the output shaft or member 22 in at least eightforward speed or torque ratios and at least one reverse speed or torqueratio. Each forward and reverse speed or torque ratio is attained byengagement of one or more of the torque-transmitting mechanisms (i.e.first clutch 26, second clutch 28, third clutch 30, first brake 32, andsecond brake 34), as will be explained below. FIG. 3 is a truth tablepresenting the various combinations of torque-transmitting mechanismsthat are activated or engaged to achieve the various gear states. Actualnumerical gear ratios of the various gear states are also presentedalthough it should be appreciated that these numerical values areexemplary only and that they may be adjusted over significant ranges toaccommodate various applications and operational criteria of thetransmission 10. An example of the gear ratios that may be obtainedusing the embodiments of the present invention are also shown in FIG. 3.Of course, other gear ratios are achievable depending on the geardiameter, gear teeth count and gear configuration selected.

To establish reverse gear, the third clutch 30, the first brake 32 andthe second brake 34 are engaged or activated. The third clutch 30connects the fifth shaft or intermediate member 52 to the eighth shaftor intermediate member 58. The first brake 32 connects the first shaftor intermediate member 42 to ground or transmission housing 50. Thesecond brake 34 connects the seventh shaft or intermediate member 56 toground or transmission housing 50. Likewise, the eight forward ratiosare achieved through different combinations of clutch and brakeengagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 10 assumes, first of all,that all the clutches and brakes not specifically referenced in a givengear state are inactive or disengaged and, second of all, that duringgear shifts, i.e., changes of gear state, between at least adjacent gearstates, a clutch or brake engaged or activated in both gear states willremain engaged or activated.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members; a first interconnecting member continuouslyinterconnecting the first member of the first planetary gear set withthe second member of the second planetary gear set; a secondinterconnecting member continuously interconnecting the third member ofthe first planetary gear set with the first member of the fourthplanetary gear set; a third interconnecting member continuouslyinterconnecting the third member of the second planetary gear set withthe first member of the third planetary gear set; a fourthinterconnecting member continuously interconnecting the second member ofthe third planetary gear set with the second member of the fourthplanetary gear set; five torque-transmitting mechanisms each selectivelyengageable to interconnect at least one of the first, second, and thirdmembers with at least another of the first member, the second member,the third member, and a stationary member; and wherein thetorque-transmitting mechanisms are selectively engageable incombinations of at least three to establish at least eight forward speedratios and at least one reverse speed ratio between the input member andthe output member.
 2. The transmission of claim 1 wherein a first of thefive torque transmitting mechanisms is selectively engageable tointerconnect the second member of the first planetary gear set with thefirst member of the second planetary gear set.
 3. The transmission ofclaim 2 wherein a second of the five torque transmitting mechanisms isselectively engageable to interconnect the third member of the firstplanetary gear set with the first member of the second planetary gearset.
 4. The transmission of claim 3 wherein a third of the five torquetransmitting mechanisms is selectively engageable to interconnect thefirst member of the second planetary gear set with the third member ofthe fourth planetary gear set.
 5. The transmission of claim 4 wherein afourth of the five torque transmitting mechanisms is selectivelyengageable to interconnect to the second member of the second planetarygear set with the stationary member.
 6. The transmission of claim 5wherein a fifth of the five torque transmitting mechanisms isselectively engageable to interconnect the third member of the thirdplanetary gear set with the stationary member.
 7. The transmission ofclaim 1 wherein the fourth and fifth torque transmitting mechanisms arebrakes and the first, second, and third torque transmitting mechanismsare clutches.
 8. The transmission of claim 1 wherein the first membersare sun gears, the second members are planet carrier members, and thethird members are ring gears.
 9. The transmission of claim 1 wherein theinput member is continuously interconnected with the second member ofthe first planetary gear set and the output member is continuouslyinterconnected with the second member of the third planetary gear setand the second member of the fourth planetary gear set.
 10. Atransmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members, wherein the input member is continuouslyinterconnected with the second member of the first planetary gear set,and the output member is continuously interconnected with the secondmember of the third planetary gear set and second member of the fourthplanetary gear set; a first interconnecting member continuouslyinterconnecting the first member of the first planetary gear set withthe second member of the second planetary gear set; a secondinterconnecting member continuously interconnecting the third member ofthe first planetary gear set with the first member of the fourthplanetary gear set; a third interconnecting member continuouslyinterconnecting the third member of the second planetary gear set withthe first member of the third planetary gear set; a fourthinterconnecting member continuously interconnecting the second member ofthe third planetary gear set with the second member of the fourthplanetary gear set; a first torque-transmitting mechanism selectivelyengageable to interconnect the second member of the first planetary gearset with the first member of the second planetary gear set; a secondtorque-transmitting mechanism selectively engageable to interconnect thethird member of the first planetary gear set with the first member ofthe second planetary gear set; a third torque-transmitting mechanismselectively engageable to interconnect the first member of the secondplanetary gear set with the third member of the fourth planetary gearset; a fourth torque-transmitting mechanism selectively engageable tointerconnect to the second member of the second planetary gear set witha stationary member; a fifth torque-transmitting mechanism selectivelyengageable to interconnect the third member of the third planetary gearset with the stationary member; and wherein the torque-transmittingmechanisms are selectively engageable in combinations of at least threeto establish at least eight forward speed ratios and at least onereverse speed ratio between the input member and the output member. 11.The transmission of claim 10 wherein the fourth and fifth torquetransmitting mechanisms are brakes and wherein the first, second, andthird torque transmitting mechanisms are clutches.
 12. The transmissionof claim 10 wherein the first members are sun gears, the second membersare planet carrier members, and the third members are ring gears.
 13. Atransmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having a sun gear, aplanet carrier and a ring gear, wherein the input member is continuouslyinterconnected with the planet carrier of the first planetary gear set,and the output member is continuously interconnected with the planetcarrier of the third planetary gear set and planet carrier of the fourthplanetary gear set; a first interconnecting member continuouslyinterconnecting the sun gear of the first planetary gear set with theplanet carrier of the second planetary gear set; a secondinterconnecting member continuously interconnecting the ring gear of thefirst planetary gear set with the sun gear of the fourth planetary gearset; a third interconnecting member continuously interconnecting thering gear of the second planetary gear set with the sun gear of thethird planetary gear set; a fourth interconnecting member continuouslyinterconnecting the planetary carrier of the third planetary gear setwith the planet carrier of the fourth planetary gear set; a firsttorque-transmitting mechanism selectively engageable to interconnect theplanet carrier of the first planetary gear set with the sun gear of thesecond planetary gear set; a second torque-transmitting mechanismselectively engageable to interconnect the ring gear of the firstplanetary gear set with the sun gear of the second planetary gear set; athird torque-transmitting mechanism selectively engageable tointerconnect the sun gear of the second planetary gear set with the ringgear of the fourth planetary gear set; a fourth torque-transmittingmechanism selectively engageable to interconnect to the planet carrierof the second planetary gear set with a stationary member; a fifthtorque-transmitting mechanism selectively engageable to interconnect thering gear of the third planetary gear set with the stationary member;and wherein the torque-transmitting mechanisms are selectivelyengageable in combinations of at least three to establish at least eightforward speed ratios and at least one reverse speed ratio between theinput member and the output member.